Attention Getting Question:
Have you ever wondered what makes things move?
Motion is all around you, even if you do not notice or see it. Motion is when something changes position, or moves. Many forces cause motion. A force is what causes an object to move. Let's explore what makes things move and how to describe the motion you see.
Have you ever pushed a toy car across the floor? If you have, you have exerted force on the toy car. Forces are usually the push or pull of one thing to another, but just because a force is exerted on an object does not mean it will put an object into motion. Balanced forces are forces that do not change an object’s motion because there is an opposing force that keeps the object in a constant state of motion. For example, if two football players push each other and cannot move, they are balanced forces.
Sir Isaac Newton was a scientist and mathematician that lived from 1643 until 1727. He studied motion and developed some ideas that we still use today. According to Newton’s First Law of Motion, an object that is motionless will stay motionless and an object that is moving will continue to move unless acted upon by an unbalanced force. An unbalanced force is a force that changes an object’s constant state of motion. If a book slides across a table, friction, one of the most common unbalanced forces, will cause the book to slow down. Friction is the force that resists two surfaces sliding together. When an unbalanced force like friction changes an object’s state of motion, it is called acceleration. Many people think acceleration only means the speeding up of an object, but an object also accelerates when it slows down or changes direction!
Newton’s Second Law of Motion states that acceleration is produced when a force acts on a mass. The greater the mass of the object, the greater the force it needs to accelerate. This law states a fundamental fact most humans already know: heavier objects require more work to move than lighter objects. This is why football linemen are so big, because they are harder to push around. Imagine trying to push a small toy car and a real car. It would be nearly impossible to push the real car and extremely easy to push the toy car!
Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction. This means when a force is applied to something, an equal force pushes back. For example, if a person is swimming in a pool and kicks off the pool’s wall, they will propel away from the wall.
Momentum is a way to describe motion. If a toy car rolls down a ramp rather than a flat surface, the car will gain momentum on the ramp to go farther than the car would on a flat surface. Momentum applies to all three laws of motion.
In summary, motion occurs when an object changes position and force causes motion. Balanced forces cancel each other out and do not cause a change of motion, while unbalanced forces cause a change in motion, or acceleration. There are laws of motion that explain how things move. Can you name the objects that are in motion around you?